Enable Config::MUS to use classic IME instead of servicified IME.

ash/mus/ash_window_tree_host_mus.cc

Index: ash/mus/ash_window_tree_host_mus.cc
diff --git a/ash/mus/ash_window_tree_host_mus.cc b/ash/mus/ash_window_tree_host_mus.cc
index 52cb894ff83f132650fd420151375c2b34959af9..371285523a74bad2c571043e618e09f36739f9ae 100644
--- a/ash/mus/ash_window_tree_host_mus.cc
+++ b/ash/mus/ash_window_tree_host_mus.cc
@@ -6,9 +6,11 @@
 
 #include "ash/host/root_window_transformer.h"
 #include "ash/host/transformer_helper.h"
+#include "ash/ime/input_method_event_handler.h"
 #include "base/memory/ptr_util.h"
 #include "ui/aura/mus/window_tree_host_mus_init_params.h"
 #include "ui/aura/window.h"
+#include "ui/events/event_sink.h"
 #include "ui/events/null_event_targeter.h"
 
 namespace ash {
@@ -84,4 +86,13 @@ void AshWindowTreeHostMus::UpdateRootWindowSizeInPixels(
   transformer_helper_->UpdateWindowSize(host_size_in_pixels);
 }
 
+ui::EventDispatchDetails AshWindowTreeHostMus::DispatchKeyEventPostIME(
+    ui::KeyEvent* event) {
+  input_method_handler()->SetPostIME(true);
+  ui::EventDispatchDetails details = SendEventToSink(event);
+  if (!details.dispatcher_destroyed)
+    input_method_handler()->SetPostIME(false);
+  return details;
+}
+
 }  // namespace ash